As image recording methods for forming an image on a recording medium such as paper based on an image data signal, there are an electrophotographic system, sublimation type and melt type thermal transfer systems, an inkjet system, etc.
With regard to the inkjet system, the printing equipment is inexpensive, it is not necessary to use a plate when printing, and since an image is formed directly on a recording medium by discharging an ink composition only on a required image area, the ink composition can be used efficiently and the running cost is low, particularly in the case of small lot production. Furthermore, there is little noise and it is excellent as an image recording system, and has been attracting attention in recent years.
Among them, an inkjet recording ink composition (radiation-curing inkjet recording ink composition), which is curable upon exposure to radiation such as UV rays, is an excellent system from the viewpoint of it being possible to print on various types of recording media because, compared with a solvent-based ink composition, the drying properties are excellent and an image is resistant to spreading since the majority of the components in the ink composition cure upon exposure to radiation such as UV rays.
Printing of flexible packaging has until now mainly been carried out by a conventional printing method such as gravure printing or flexographic printing. However, in recent years digital printing, to meet the increase in small lot printing, has been attracting attention in the field of flexible packaging also. In the case of digital printing, it is unnecessary to make a plate, it is also unnecessary to carry out color matching, and in the case of small lot printing in particular it is possible to achieve a low cost and, moreover, since the preparation time can be cut it results in a reduction in printing time.
Examples of conventional inkjet recording methods include those described in JP-A-9-175009 (JP-A denotes a Japanese unexamined patent application publication), JP-A-2012-125978 or JP-A-2005-238035.